The present invention concerns fuel briquettes based upon substantially solid fuels such as hard coal, coke, brown coal, wood coal and the like, which in the presence of synthetic organic compounds as binding agent and under employment of a further additive are obtained by means of briquettization, as well as a process for the production of such fuel briquettes.
It is known to manufacture briquettes by means of pressing of powder shaped or fine-grained or course-grained or in some other such manner particulated fuel material.
A series of fuel materials already naturally possess a binding agent, e.g. brown coal, other types of coal, e.g. anthrecite or mixtures of anthrecite with other types of coal must, however, still have added a binding agent in connection with the briquettization operation, in order that there may result briquettes which display a sufficient content of the fuel material and therewith also sufficient strength and a corresponding firing behavior.
The addition of the binding agent should however not only increase the holding together of the briquetted material, so that in connection therewith a better handleability of the briquettes is possible, but it should also improve the briquette character of the pressed material during the briquettization operation per se, e.g. in order to make possible a better plasticization during the shaping process. Moreover, the additives should favorably influence the burning behavior of the fuel material such as the efficiency upon combustion, the formation of exhaust and the like as much as possible.
In both patent and also otherwise technical literature there have already been described numerous binding agents, which are supposed to be employed upon the briquettization of coke, anthracite, mager- or so-called fat coal or coal mixtures and the like.
The previously known techniques display, however, disadvantages, from different points of view. Thus, for example, the use of pitch and asphalt bitumen as binding agent leads to briquettes which upon combustion, smoke strongly and disintegrate too quickly on account of softening of the binding agent. This leads u.a. to the result that upon combustion the material present is not completely utilized and leaves noticeable in the ash a still very great amount of non-combusted coal material.
Hard coal tar pitch as binding agent has the disadvantage that it occurs containing carcinogenic substances therein. Accordingly, this use should be avoided as much as possible. The employment of pitch is therefore forbidden as binding agent for briquettes which are supported to serve as houshold-type material, for reasons of enviromental protection. For example, according to the federal emissions protection laws of 1976 in West Germany, such briquettes can only be employed in ovens of the type which an after-combustion of the exhaust gas occurs.
In Gluckauf-Forschungshefte 36 (4) 156-61 (1975) numerous synthetics are mentioned which have been employed as binding agent for the production of hard coal briquettes. It is there maintained that aqueous dispersions of synthetics (plastics and the like) lead to briquettes with "Russ" tar numbers lying above 300 and thus cannot be spoken of as low-exhaust briquettes, for which it is indicated, must possess a "Russ" tar number below 200.
For an entire series of synthetic materials further cited therein, the relatively higher portion of the synthetic material is necessary, in order to obtain a sufficient binding of the fuel material in connection with the briquettization technique. With several of the there-mentioned synthetic materials it is difficult to obtain a sufficiently homogeneous inter-mixing of fuel material and binding agent. It is also necessary in a series of instances to employ mixtures of different coals. Finally, several of the there-mentioned synthetics require yet an addition of a further organic adjuvant, e.g. an addition of oil. Moreover, several of the there-given synthetic materials have a tendency to form upon combustion gas, which can lead to odor problems.
DE-0S3114141 describes a co-use of polyvinyl alcohol as synthetic binding agent. According to the teachings of this reference, however, a still cationic polyurethane is employed, so as to obtain sufficient strength. The initial strengths of the there-described fuel briquettes likes, as a rule, relatively low.
It is common to all the previously mentioned compositions that the sulphur present in the fuel material is not sufficiently retained during the combustion whereby the result can be that a large part can be let into the atmosphere with the combustion gas in the form of gaseous sulphur compounds, such as sulphur dioxide.
Whether or not numerous techniques are already known for the manufacture of fuel briquettes using binding agents and other such additives, there exists still a need for improved processes for the production of fuel briquettes, which processes result in briquettes having favorable chemical characteristics and advantageous burning behavior, and the combustion gas of which contained less substances that can lead to an environmental burden.